Recently, I wanted to read some documents (i.e. from Google Docs) on my Kindle. I was interested in exporting .mobi, as reading PDFs on Kindle is really annoying.
I found converting .doc into .mobi not a trivial task. Luckily, nearly everything is possible in Ubuntu with a few steps:

I’m using several external drives for backup purposes. I was interested whether there are some differences in terms of read/write/access time between these. I have tested two drives connected directly to USB3.0 port and through USB3.0 hub:

There are two interesting results. First of all, there is no speed difference between both drives (read/write/access: 83MB/49MB/17ms). Thus buying super-performance (read super-expensive) external drive make no sense, as the drive speed will be limited most likely by USB3.0 port connection anyway.
Secondly, there is no speed difference if drive is attached directly to the computer USB3.0 or through USB3.0 hub. But, I have noticed mouse lags when mouse was connected through the same USB hub. Thus if you expect to perform extensive disk reads/writes it’s better to connect it directly to the computer or at least avoid many important devices to use the same hub.

I’m preparing Ubuntu image for the course. After installation of required software and datasets, the system image grew a lot. I have decided to shrink its size by disabling swap and removing unused data. But the system image didn’t shrink automatically after removal of the files. You need to do it manually:

Run your system from LiveCD

Install zerofree and free unused space

sudo apt-get install zerofree
# 10min
sudo zerofree -v /dev/sda1

In the host system, release and remove the image from VirtualBox (but keep it in the filesystem!)

And compact image size

VBoxManage modifyhd Ubuntu1404/Ubuntu1404.vdi --compact&lt;/code&gt;

Finally, you will have to add .vdi image back to VirtualBox machine.

In my case, the .vdi image shrunk from 7.2G to 6.2G (exactly the released size under Ubuntu), so I think it’s worth the effort.

Finally I had some time to get my hand on new Raspberry Pi 2.
I think it’s useful to access the RPi2 by ssh (work out of the box) and NX. Installation of NX server is quite time-consuming, but I think it’s worth to give it a try! Here is what I did: